This invention relates to lenses and more particularly to lenses incorporating polarizing films or coatings and processes of making such lenses utilizing oxide additives that have distinct transmission and absorption qualities.
One challenge faced by lens manufacturers concerns glare. The term glare refers to the presence of one or more areas in the field of vision that are of sufficient brightness to cause an unpleasant sensation, a temporary blurring of vision, or a feeling of ocular fatigue. Glare occurs when patches of bright light are reflected from smooth, shiny surfaces into the eye. Typical reflecting surfaces include water, snow, roadways and glass. Reflections are not only annoying but interfere with vision, at times seriously.
It takes more than regular sunglasses to protect a person from the discomfort and vision-depleting effects caused from glare. Tinted lenses or other filters are of little help in controlling disability or discomfort glare. If a hot spot in the visual field is ten times as bright as the background illumination, the use of a filter with 50% transmittance is of little help in the visual field, because both the hot spot and the background are reduced by the same percentage. However, light-polarizing lenses are useful in controlling glare because they filter only polarized light, and directly-reflected sunlight is polarized, while ambient lighting is not.
Another challenge faced by lens manufacturers concerns light reflecting off the lens itself. When light reaches the boundary between two transparent media having different indices of refraction, most light is refracted, but a small amount is reflected. Reflected light may be troublesome because it can produce ghost images, falsification of image position, haze and loss of contrast of images being viewed through a lens. Reflected light can reduce transmission up to 12% on certain lens materials.
Applying an anti-reflection (AR) coating on the front and back surface of a lens can increase the transmittance of light to over 99%. Unfortunately, anti-reflective coatings are relatively soft and tend to scratch easily. In addition, they tend to display greasy marks and smudges and require frequent and careful cleanings. The more effective the AR coating (greater transmission), the greater the chance that lens surface imperfections will be seen.
To increase the hardness of a coating and to make marks less noticeable and the surface easier to clean, hydrophobic coatings are applied. A hydrophobic coating is a special layer (usually silicon) placed on top of an anti-reflective coating. The hydrophobic coating is a smooth, flexible layer, which fills in the pores in the surface of the anti-reflective layers. This final hydrophobic layer creates a hard slick surface giving the lens greater scratch resistance, water-repellant features, and easier cleaning capabilities.
A third and even more complex challenge faced by designers of sunglasses is to maintain the wearer""s ability to distinguish objects based on color.
Radiation is a physical term defining the transfer of energy through space, from an emitter or radiator to a receiver. When light is emitted by a source and is subsequently absorbed by a receptor, a net transfer of energy occurs. The sun is a radiator, producing energy that radiates through space in all directions. The sun""s radiation is called electromagnetic radiation because it consists of an oscillatory electric field and of an oscillatory magnetic field which are perpendicular to one another and to the direction of propagation of the radiation. This radiation consists of minute particles called photons. The distance of measurement between one oscillation of one photon is called a nanometer (nm). A single photon can differ from another photon in only one respect: its energy. A high value of this nm measurement denotes considerable sluggishness and so implies a low frequency of oscillation and a low energy. A photon of shorter wavelength oscillates more frequently and carries more energy. And to these differences in energy our eyes respond, enabling us to see colors High-energy light, in which most of the photons have wavelengths of around 400 nm looks blue or violet, while low-energy light, containing photons mainly of wavelengths around 700 nm, looks red. The light that is sensitive to humans lies within the visible spectrum. The visible spectrum consists of several colors that have different levels of energy. This is illustrated in FIG. 1 of the drawings, which shows the electromagnetic spectrum.
The following Table 1 shows the correspondence between energy levels and human color sensation:
Studies conducted in connection with the manufacture of artificial lighting have found that human color vision may be characterized chromatically by three channels. Chromatic response falls nearly to zero in the blue-green near 500 nm and in the yellow near 580 nm, as well as in violet beyond 400 nm and in the deep red beyond 700 nm. The minima may be related to the fact that the red-green-blind protanope sees no hue at all near 500 nm and the tritanope sees no hue near 580 nm. These wavelengths impair proper identification of chromaticities of colored objects. The eye uses wavelengths near 450, 540, and 610 nm most effectively, and in a sense samples, at these wavelengths, all incoming light. Color discrimination can be improved by elimination of wavelengths near 500 and 580 nm,1 increasing color discrimination per watt input at the eye.2 
1Journal of the Optical Society of America, Volume 62, Number 3, Pages 457 through 459. 
2Journal of the Optical Society of America, Volume 61, Number 9, Pages 1155 through 1163. 
According to the invention, a lens has a layer that includes an oxide additive resulting in a relatively high light transmittancy at 450 nm, 540 nm, and 610 nm, and a relatively low light transmittancy at 500 nm and at 580 nm. Including a layer having such properties in a lens along with a polarizing filter can result in a particularly useful lens.